Field of the Invention
The present invention relates to a direction finding receiver contained in a hand held portable housing with a ferrite rod antenna for direction finding an rf signal source.
Description of the Prior Art
In the field of direction finding receivers, it has been the general practice in the art to employ a ferrite rod antenna to direction-find the rf signal source by rotating the ferrite rod antenna until a null is obtained in the signal level. Such receivers have been unsatisfactory in the past in that the receivers are not hand held portable units. Further, it has been necessary to know the exact rf signal frequency so that the receiver can be tuned to the rf signal source frequency before the signal source can be direction found. Also, the rf amplifiers in the receivers are highly sensitive not permitting direction finding of nearby rf signal sources. Therefore, when a signal source is to be direction found, it is necessary to use a bulky receiver which has to be tuned to the exact rf signal source frequency before the ferrite rod can be rotated to find a null in the signal level. Further, if the rf signal source frequency is not known or falls outside of the receiver bandspread, then it is not possible to direction find the rf signal source. If the signal source is nearby, the rf amplifier is usually overloaded by the rf signal source. U.S. Pat. No. 3,323,129 issued to Held discloses a receiver with a ferrite rod antenna that pivots on top of the receiver cabinet. To direction find an rf signal source, it is first necessary to know the rf signal frequency so that the receiver can be tuned to that frequency. The antenna is then rotated to find the null. In FIG. 3, the ferrite rod antenna pivots, and when a null is obtained in the signal level, the axis of the ferrite antenna rod indicates the direction of the rf signal source to be direction found. U.S. Pat. No. 3,683,384 issued to Warren discloses a hand held portable directional receiver which utilizes fixed single frequency rf modules which are precisely tuned to the signal frequency of the radio beacon to be direction found.